The present invention relates in general to solution mixing systems, and is particularly directed to a new and improved solution preparation apparatus, that is operative to controllably mix, store and supply a fluid containing a component diluted to a prescribed concentration, such as a diluted saline solution used for the transport of blood cells in a hematology analyzer.
Systems employed for particulate sample analysis, such as, but not limited to, those employed in medical applications to analyze particles such as blood cells, customarily include, or are coupled with, some form of sample delivery and mixing apparatus, that prepares a respective sample, namely, places it in the physical condition necessary for acceptance and processing through a measurement flow channel of a measurement instrument. Achieving the appropriate physical condition typically involves suspending and separating the particles in a fluid that is injected into a fluid transport channel for delivery to the particle measurement (e.g., optical illumination-based) subsystem.
For example, in the case of a hematology analyzer, a prepared blood sample carrier fluid typically comprises an isotonic solution having a prescribed dilution ratio of concentrate (e.g., sodium chloride) to diluent (e.g., deionized (DI) water). A blood sample which is to be analyzed is dispensed and delivered to an input sample reservoir (for example by way of a sample-retaining test tube, or the like). The blood sample is combined with the blood sample carrier fluid. A surfactant may also be mixed into the solution in order to readily disperse the particles.
With the development of automated (computer workstation-controlled) cell analyzers, there is currently a high demand for complete, yet reasonably priced instruments that not only occupy a relatively limited amount of user space, but also are capable of high throughput and reduced operating time. One of the requirements of such systems is that they provide a continuous supply of a blood sample carrier fluid using a minimum amount of labor or floor space. In addition, there is a need to have the blood sample carrier fluid with mixture uniformity. Moreover, the blood sample carrier fluid must be compatible with test procedures for analyzing the blood sample. Still further, the system should provide safety measures for the blood sample carrier fluid storage, delivery and disposal.
In accordance with the present invention, a new and improved solution preparation and delivery architecture is provided which is operative to controllably mix, store and deliver to one or more utility devices, such as blood sample analyzing instruments, a solution of a diluent, such as deionized water, containing a prescribed concentration of a dispersed or dissolved component, such as sodium chloride. For this purpose, the solution preparation and supply apparatus includes a diluted solution mixing container, that is coupled to receive, mix and store each of a liquid concentrate of a prescribed component and a diluent. The liquid concentrate is stored in and extracted from a concentrate storage container, under the control of a supervisory processor, for delivery over a concentrate transport path to the solution mixing container.
The concentrate transport path includes a set of valve and pump components, that enable it to controllably recirculate the liquid concentrate contents of the component storage container, in order to maintain the concentrate in a homogenous state prior to its being supplied to the solution mixing container. The diluent is supplied to the mixing tank by way of a diluent transport path, coupled to a source of diluent, such as deionized water, and is configured to controllably dispense the diluent into the mixing container. To avoid the potential problem of having an unused diluent distribution line serve as a host for the growth of biological contaminants, the diluent transport path is controllably purged of potential contaminates prior to supplying the diluent to the mixing container.
A mixed solution transport path is coupled to the solution mixing container and to a prepared solution output port. The mixed solution transport path actively recirculates and thereby homogenizes the contents of the mixing container, during an iterative sequence of adding diluent to the mixing tank and conducting conductivity measurements, until the conductivity of the solution in the mixing tank reaches a target value required by a downstream instrument. The mixed solution transport path is also configured to controllably actively pump out solution that has been mixed and stored in the mixing container. The output port is coupled over a mixed solution supply line to one or more solution on demand storage reservoirs for respective instruments.
A demand valve-responsive reservoir for a respective instrument is coupled to the prepared solution supply line and may be configured as an industry standard CUBITAINER(copyright) plastic container (Hedwin Corp., Baltimore, Md.). A demand controller manages delivery of the mixed solution from the mixing container to the reservoir when its associated instrument (e.g., hematology analyzer) requires additional (saline) solution. Because the reservoir is expected to remain connected to an instrument for a long period of time, it is placed in a protective tray. The tray contains leak detectors, that monitor whether the outside of the reservoir is damp, contains a minor leak, or whether a massive leak has formed. A leak condition is determined by measuring whether the impedance between sensor pairs is less than a prescribed value.
An auxiliary (waste) tank may be coupled to the fluid transport paths for the solution mixing tank storing purged waste liquid, to accommodate the case where the facility in which the mixing tank is installed has no readily accessible floor drain for the purpose.
The preparation, mixing and delivery sequence executed by the invention employs a plurality of conductivity thresholds to reach a target solution conductivity associated with desired (saline) concentration. This enables the invention to comply with a solution specification, such as a constant conductivity isotonic solution for a hematology analyzer, that uses changes in conductivity of a fluid in a flow measurement aperture to count and recognize blood cells.